Acidic solutions have been used in the dental field for years to partially decalcify enamel to enhance mechanical attachment for dental fillings. Similar treatment of dentin to enhance mechanical and/or chemical adhesion of dental restorative materials is also well-known to those skilled in the art.
Although use of the foregoing procedures have resulted in a great deal of success in restoring teeth with significant degrees of permanence, microbial influences on teeth and dental restorative materials remains a significant concern for the dental practitioner and the patient. Tooth decay and the pathology of dental pulp are caused by bacterial organisms and their metabolic byproducts. The effectiveness of dental restoratives in replacing dental structures lost by decay is decreased by reinfection beneath and around the dental restoration site. Such reinfection is not uncommon clue to the abundance of bacterial organisms in the oral cavity. It is, of course, not possible to totally eliminate all such organisms from the oral cavity or the site under restoration in the patient. The structure and nature of the restoration may also contribute to the increased likelihood of such reinfection, particularly where the restoration presents physical obstacles to tooth cleaning and maintenance.
A number of procedures have been developed to attempt to reduce bacterial infection of prepared and restored teeth. The chemical versions of such treatments have included use of dentifrices, mouthwashes or other topical applications of solutions containing antimicrobial agents. See, e.g., U.S. Pat. Nos. 4,839,158; 5,180,577; RE 31,397.
The above-cited references disclose a variety of antimicrobial agents including chlorohexidine [1,1-hexamethylene bis[5-(4 chlorophenyl)-biguanide] and benzalkonium chloride (alkyl benzyl dimethyl ammonium chloride) (See U.S. Pat. Nos. 4,839,158: 5,180,577). However, use of such agents is reported as problematic due to their undesirable side effects. For example, both compounds are reported to stain teeth, a highly undesirable result in dental restorative procedures (U.S. Pat. No. 4,839,158). Chlorohexidine is also reported as unstable, its precipitation from solution causes a marked decrease in its antimicrobial properties (See U.S. Pat. No. 5,180,577).
The aforesaid patents report addressing these problems by either avoiding use of chlorohexidine and/or benzalkonium chloride (U.S. Pat. No. 4,839,158) or by adding anti-staining and/or stabilizing agents to the antimicrobial solution (U.S. Pat. Nos. RE 31,397, 5,180,577). However, none of these references disclose or suggest use of antimicrobials in conventional restorative procedures involving partial decalcification or etching of the tooth dentin or enamel. Such conventional procedures typically involve several steps. First, the undesired tooth tissue is removed by drilling or other procedures. Second, the etchant is applied topically in an aqueous solution, allowed to remain in contact with the tissue for a minute or less, and removed by water rinsing. The restorative material is then applied and self-cured or hardened by external agents such as ultraviolet light and/or light in the visible spectrum. Adding the aforementioned reference's topical application solutions as a separate step to the restorative process is undesirable because it increases the complexity of the procedure and time spent by both the dentist and the patient in the dental office.
Applicant believes he was the first to explore use of antimicrobials in combination with etchants in restorative procedures. The initially chosen antimicrobial, chlorohexidine, in combination with phosphoric acid etchant, exhibited prolonged antimicrobial activity. See Chan et al., J. Dent. Res., 71, (AADR Abstracts) #284 (1992). However, applicant experienced the above-reported instability problems with chlorohexidine, i.e., after several months, the antimicrobial began to precipitate from solution. As indicated above, that undesirable side effect has been reported in the literature as causing a decrease in reported antimicrobial activity.
There exists, therefore, a need in the art for stable antimicrobial etchant agents which can be readily incorporated into dental restorative procedures and which exhibit prolonged antimicrobial activity.